The subject matter of the present disclosure broadly relates to the art of elastomeric articles and, more particularly, to a replacement indicator for elastomeric articles as well as elastomeric articles (e.g., gas spring assemblies and pneumatic tires) that include a replacement indicator and methods of manufacturing the same.
The subject matter of the present disclosure may find particular application and use in conjunction with components for wheeled vehicles, and will be shown and described herein with reference thereto. However, it is to be appreciated that the subject matter of the present disclosure is also amenable to use in other applications and environments, and that the specific uses shown and described herein are merely exemplary. For example, the subject matter of the present disclosure could be used in connection with non-wheeled vehicles, elastomeric components for support structures, height adjusting systems and actuators associated with industrial machinery, components thereof and/or other such equipment. Accordingly, the subject matter of the present disclosure is not intended to be limited to use associated with elastomeric components of wheeled vehicles.
Wheeled motor vehicles of most types and kinds include a sprung mass, such as a body or chassis, for example, and an unsprung mass, such as two or more axles or other wheel-engaging members, for example, with a suspension system disposed therebetween. Typically, a suspension system will include a plurality of spring devices as well as a plurality of damping devices that together permit the sprung and unsprung masses of the vehicle to move in a somewhat controlled manner relative to one another. Movement of the sprung and unsprung masses toward one another is normally referred to in the art as jounce motion while movement of the sprung and unsprung masses away from one another is commonly referred to in the art as rebound motion.
Known gas suspension systems, such as for use on vehicles, for example, normally include one or more gas spring assemblies that utilize a flexible sleeve or bellows that is formed from elastomeric material. In many cases, the flexible sleeve or bellows will be formed from one or more layers or plies of elastomeric material (e.g., rubber) with one or more layers or plies of reinforcing material embedded therein. Regardless of the construction, however, the flexible sleeve or bellows at least partially defines a spring chamber that contains pressurized gas and permits the gas spring assemblies to support a load.
As a result of the relative movement between the sprung and unsprung masses of a vehicle, gas spring assemblies are routinely displaced between extended and compressed conditions, which results in repeated bending and unbending of the flexible sleeve or bellows. Furthermore, known gas suspension systems typically provide the capability of adjusting the height and/or alignment (i.e., leveling) of a sprung mass (e.g., a body or chassis of a vehicle) relative to an unsprung mass thereof (e.g., a wheel-engaging member or axle housing of the vehicle). Such actions can result in additional bending and unbending of the flexible sleeve or bellows of the gas spring assemblies.
Elastomeric devices, such as flexible sleeves and bellows, for example, may, under some conditions, experience a decrease in performance and/or other characteristics as a result of such cyclical flexing (i.e., bending and unbending) and/or as a result of exposure to certain environmental conditions and/or agents, or as a result of a combination of these factors. As such, it may be desirable, in some cases, to identify and/or assist in predicting the occurrence of such decreases in performance and/or other characteristics, whether presenting suddenly or gradually over an extended duration.
Environmental agents, such as have been referenced above, can include chemical agents (e.g., oxygen (O2), ozone (O3), volatile organic compounds, etc.) and/or physical agents (e.g., heat, such as may disadvantageously increase the rate of oxygen (O2) degradation). Ozone, in particular, has been identified as contributing to performance loss in elastomeric articles. In some cases, cumulative exposure to ozone, particularly when occurring over a prolonged duration, can contribute to the degradation of many rubber compounds. Since performance loss due to ozone exposure is typically a slow process, any performance loss may not be visually identifiable in some elastomeric articles until after the useful lifetime of the elastomeric article has expired.
Accordingly, it is believed desirable to develop a replacement indicator for elastomeric articles, as well as elastomeric articles that include such replacement indicators and methods of manufacturing the same.